Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2000-03-21
2002-04-23
Gibson, Roy (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C607S101000, C607S102000, C606S009000
Reexamination Certificate
active
06375672
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a method for strengthening collagen in collagenous tissue which uses the controlled application of heat to induce shrinkage or contraction of the collagen in the tissue and a cross-linking means which cross-links the shrunken collagen in the tissue thereby stabilizing the strengthened, collagenous tissue. In particular, the present invention relates to an in vivo method for treating joint instability problems, controlled manipulation of skin structure and properties, and other problems involving collagen-containing tissues. The present invention further relates to an in vitro method for stabilizing collagenous tissue for use in vivo or in vitro. Further, the present invention relates to a method for treating collagenous tissue and testing the strength and stability of the treated tissue.
(2) Description of Related Art
Glenohumeral instability caused by shoulder capsular redundancy, glenohumeral joint laxity, and excessive joint volume, for example, is a problem affecting approximately 8% of the population. Kinematically, the problem may be defined as the inability to maintain the humeral head (the ball) centered in the fossa (the socket) caused by the pathological redistribution of the forces that keep the joint in equilibrium.
Redistribution of the forces are generally initiated by soft tissue problems. These can occur from a single acute event that disrupts the capsule, recurrent microtrauma that damages the biological microstructure of the joint capsule or a traumatic ligamentous laxity. The result is that the soft tissue allows for excessive motion of the joint surfaces in directions not normally permitted by the ligaments or capsule surrounding the joint.
This problem is generally seen in athletes and the young. In the milder cases, symptoms include shoulder fatigue, weakness and pain while repetitive dislocation and subluxation and even the loss of motion are indicative of more severe cases.
Currently applied treatments for glenohumeral instability include closed techniques, open techniques, and arthroscopic techniques. Closed techniques which are based on exercise depend on strengthening the muscle group that surrounds the shoulder joint. In addition to relatively long treatment period (6 to 12 months), the high reoccurrence rate limits their application as a stand alone method (Hayashi et al., Am. J. Sports Med. 25: 107-112 (1997)). The success in treatment of mild cases is only about 20% (Burkhead et al., J. Bone Surg. 74A: 890-896 (1992).
Open techniques generally involve operative procedures and the method applied depends on the type of instability, i.e., anterior, posterior or multidirectional. It has been reported that approximately 300 different operative procedures have been applied for the surgical management of instability (Zayne et al., Clin. Sports Med. 14: 863-883 (1995)). In addition to being technically difficult, these operations which are performed for the capsule shift or repair are generally known to result in pain and have the potential to reduce range of motion and even cause loss of motion, nerve injury and osteoarthritis (Bana et al., Sports Med. Arthroscopy Rev. 1: 242-248 (1993); Bigliani, Techn. Orthop. 3: 36-45 (1989); Jobe, Techn. Orthop. 3: 29-35 (1989)). Only 30% of patients undergoing surgical operations for glenohumeral instability appear to achieve their pre-injury function.
Arthroscopic techniques generally pose less risk of neuromuscular injury and typically involve a shorter rehabilitation period compared to open techniques. While arthroscopic techniques have less risk of neuromuscular injury and require a shorter rehabilitation period than other techniques, these techniques require extreme technical expertise and are very much dependent on the skill of the surgeon. Furthermore, in many cases, the repair effected by arthroscopic techniques is short-term since reoccurrence rates as high as 50% have been observed. As such, alternatives to the foregoing techniques are highly desirable.
Recently, arthroscopic thermotherapy has begun to be applied for the treatment of glenohumeral instability problems. The therapy aims to reduce the excessive capsular volume and ligamentous laxity by heating the articular surfaces of the glenoid and the humeral head, a method otherwise referred to herein as heat assisted capsular shift procedure. Arthroscopic thermotherapy techniques for contracting collagen fibers in soft tissue to increase rigidity of the tissue have been the object of several U.S. Patents.
U.S. Pat. No. 5,591,157 to Hennings et al. discloses an apparatus and method for tightening the tympanic membrane by using a laser to apply heat to the collagen fibers of the membrane. The heat causes the collagen fibers to contract which tightens the membrane.
U.S. Pat. Nos. 5,569,242 and 5,458,596 to Lax et al. discloses an apparatus and method for strengthening the collagenous tissue in the joint to stabilize the joint by the controlled contraction of the collagen tissue. The apparatus provides thermal energy to the soft tissue which causes the collagen fibers to contract or shrink thereby improving the stability of the joint.
Although results of short term follow ups show that arthroscopic thermotherapy is promising with relative few side effects, questions about the long term effect remain unanswered. Improved range of motion of the repaired shoulder, accelerated patient healing, as well as lower recurrence rates are the major advantages of this therapy. The disadvantages are the time dependent decrease of tissue stiffness, over-stiffening or excessive drop in tissue strength in cases of overexposure to heating, and the trend for relaxation of the treated tissue back to its untreated length. This kind of response has also been observed in most of the research done using animal models (Chen and Humphrey, J. Biomechanics 31: 211-216 (1998); Chen et al., IEEE Trans. Biomed. Eng. 45: 1234-1240 (1998); Shaefer et al., Am. J. Sports Med. 25: 841-848 (1997)). Time-dependent changes in the mechanical properties and behavior of the treated tissue are thought to be the major reason for recurrence and thus, failure of the therapy in the long run. A further disadvantage with currently proposed arthroscopic thermotherapy is that the success of the therapy completely depends on subjective parameters such as the visual perception, experience, and judgment of the surgeon. Thus, while arthroscopic thermotherapy appears to be an advancement in the art, understanding the phenomena involved in tissue response is incomplete and because of recurrence, improvements are clearly needed.
There are other methods known in the art for modifying collagen. For example, chemical modification of collagen films and collagenous tissues using cross-linking agents such as glutaraldehyde, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, hexamethylene diisocyanate and diphenylphosphorylazide which induce inter/intramolecular bonds have been used for fixation in histological examinations (Simionescu et al., J. Biomed. Mater. Res. 25: 1495-1505 (1991)), controlled drug release (Gohel and Amin, J. Controlled Release 51: 115-122 (1998)), delaying the in vivo degradation of (Lynn et al., J. Biomed. Mater. Res. 24: 1185-1201 (1990)), and suppressing the recipient immune response (Gade et al., J. Biomed. Mater. Res. 25: 799-811 (1991)) to soft tissue xenografts like porcine heart valves and arteries. On the macro scale, the effects of these modifications are known to be pronounced with respect to viscoelastic behavior and mechanical properties like stiffness and toughness (Finger et al., Arch. Ophthalmol. 105: 716-718 (1987); Lee et al., J. Biomed. Mater. Res. 28: 981-992 (1994); Davidson, Conn. Tissue Res. 18: 293-305 (1989); Naimark et al., Biorheology 35: 1-16 (1998)) as well as with respect to the denaturation temperature (Ruijrok et al., J. Mater. Sci. Mater. Med. 5: 80-87 (1994); Horgan et al., Arc. Biochem. Biophys. 281: 21-26 (1
Aksan Alptekin
McGrath John J.
Board of Trustees of Michigan State University
Gibson Roy
McLeod Ian C.
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